How Dangerous Are Venomous Snakes in America?

J. Whitfield Gibbons and Mike Dorcas

OVERVIEW

People's attitudes toward natural environments are a primary determinant of how they address environmental issues. Negative perceptions about particular components associated with natural ecosystems presumably result in diminished support for or protection of the system or components held in low esteem. For example, some individuals fear or hold contempt for southern swamps, an attitude due in part to an association between swamps and the organisms they harbor, such as snakes and alligators. The bases for an irrational fear of snakes (ophidiaphobia) are presumably grounded in the fact that some snakes indeed are venomous and a few can cause serious injury or death in humans. Because venomous species are among the more spectacular and sometimes largest snakes in some regions, they understandably serve as the representative species of the group for some people who may otherwise be ignorant of the suborder Serpentes, which includes appreciably more species that are harmless than venomous. In the United States the potential for serious snakebite from native species in natural settings is overrated by most individuals, including field ecologists. Several statistics are available to indicate the low probability of serious injury or death from "legitimate snakebite" (one in which the victim is bitten by a non-captive venomous species without being aware of the presence of the snake) in a natural setting. Most snakebites in the United States are caused by individuals who are attempting to catch, kill, or handle the snake, often a captive specimen. The probability of death from snakebite annually in the United States is miniscule.

The recent documentation that U.S. pit-vipers can control the amount of venom injected based on prey size is partial explanation for the low mortality from legitimate snake bites, particularly "dry bites," in which no venom is injected into the victim. If snakes are able to control the quantity of venom injected in striking prey, then presumably they would be capable of controlling the quantity injected in defense against a predator or human. Presumably venom is biologically expensive, a commodity that a snake would be reluctant to dispense needlessly. A strike with injection of a minimal quantity of venom would be as effective at temporarily warding off most larger animals as a large supply of venom. Circumstantial evidence for controlled venom release by snakes is apparent in the numerous bites of hunting dogs in the southeastern United States. Preliminary surveys reveal that countless dogs are bitten annually in the Southeast, usually on the face or shoulders, by venomous snakes, but few dogs die from the experience. Although a partial immunity of dogs to snake venom is a possible explanation for this observation, we believe the more likely explanation is that venom release has been controlled by the snake so that attention-getting, but non-lethal, doses are delivered. An additional way to conserve venom is not to strike at all.

A researcher stepping on a cottonmouth

With the help of a mechanical hand, a researcher picks up a cottonmouth.

OBJECTIVES

The objective of our study is to determine the defensive behavior of common venomous snakes. We will provide snakes opportunity to strike defensively under three habitat conditions (open encounter of previously uncaptured snake in natural habitat situation, encounter of snake in experimental enclosure, and encounter in laboratory) and under three human postural conditions (standing alongside snake within striking distance, restraining snake for two seconds by standing on it, restraining snake for twenty seconds by standing on it, and picking the snake up). Obviously protective foot, leg, hand, and arm gear will be worn by the human subjects involved in the experiments.

The following species will be used in the experiments: cottonmouth, copperhead, diamondback rattlesnake, canebrake rattlesnake, and pygmy rattlesnake. The cottonmouth will be the primary species of focus initially because of their abundance in the region.

All participants in the study have extensive experience in working with snakes in both field and laboratory. They include:

Whit Gibbons has written five books on herpetology, writes a weekly environmental column distributed by the New York Times Regional Newspaper group to more than 30 newspapers, and in 1995 was awarded the State of South Carolina Environmental Awareness Award by Governor Beasley. (complete biography enclosed)

Tony Mills is the Environmental Education Coordinator at SREL, gives approximately 250 presentations each year to schools, civic groups, and other organizations, and oversees the extensive wildlife collection at SREL.

David Scott has published two major scientific papers on cottonmouths and was the co-author of and photographer for the REPTILE AND AMPHIBIAN STUDY merit badge booklet published by Boy Scouts of America (1994).

Kurt Buhlmann is a graduate student in herpetology who formerly worked for the Virginia Heritage program and has many years experience working with venomous reptiles.

Mark Mills was graduate student at the University of Georgia. His PhD research focused on ecology of the brown water snake (Nerodia taxispilota). In his research he captured and marked more than 1200 brown water snakes in the most extensive study ever conducted on the species.

Michael Dorcas is an assistant professor at Davidson College and a visiting researcher at SREL. He conducted his doctoral dissertation on rubber boas in Idaho and was a post doctoral fellow at SREL for several years.